import type { Metadata, MetadataRoute } from "next";

/** Production origin used for `metadataBase`, canonical resolution, and sitemap URLs. */
export const PRODUCTION_SITE_ORIGIN = "https://communityrule.com";

const INDEXABLE_HOSTS = new Set([
  "communityrule.com",
  "www.communityrule.com",
  "communityrule.info",
  "www.communityrule.info",
]);

export const NO_INDEX_ROBOTS = { index: false, follow: false } as const;

function hostnameFromHostHeader(host: string | null | undefined): string {
  if (!host) return "";
  return host.split(",")[0]?.trim().split(":")[0]?.toLowerCase() ?? "";
}

function isLoopbackHost(hostname: string): boolean {
  return (
    hostname === "localhost" ||
    hostname === "127.0.0.1" ||
    hostname === "0.0.0.0" ||
    hostname === "::1"
  );
}

/**
 * Prefer the public hostname Cloudron's proxy forwards. Standalone binds
 * `0.0.0.0`, which is not a crawlable host — fall back to `CLOUDRON_APP_ORIGIN`.
 */
export function resolveRequestHost(
  forwardedHost: string | null,
  host: string | null,
): string | null {
  if (forwardedHost) {
    const first = forwardedHost.split(",")[0]?.trim();
    if (first) return first;
  }

  if (host) {
    const hostname = hostnameFromHostHeader(host);
    if (!isLoopbackHost(hostname)) return host;
  }

  const origin = process.env.CLOUDRON_APP_ORIGIN?.trim();
  if (origin) {
    try {
      return new URL(origin).host;
    } catch {
      return host;
    }
  }

  return host;
}

/**
 * Staging, restore-drill hosts, and local dev are not indexed. Override with
 * `SITE_INDEXING=true` / `false` when the hostname check is not enough.
 */
function isIndexableHost(host: string | null | undefined): boolean {
  const override = process.env.SITE_INDEXING?.trim().toLowerCase();
  if (override === "true") return true;
  if (override === "false") return false;
  return INDEXABLE_HOSTS.has(hostnameFromHostHeader(host));
}

function canonicalPath(pathname: string): string {
  const trimmed = pathname.trim();
  if (trimmed === "" || trimmed === "/") return "/";
  const withLeading = trimmed.startsWith("/") ? trimmed : `/${trimmed}`;
  const withoutQuery = withoutQueryOrHash(withLeading);
  if (withoutQuery.length > 1 && withoutQuery.endsWith("/")) {
    return withoutQuery.slice(0, -1);
  }
  return withoutQuery;
}

function withoutQueryOrHash(pathname: string): string {
  const q = pathname.indexOf("?");
  const h = pathname.indexOf("#");
  let end = pathname.length;
  if (q !== -1) end = Math.min(end, q);
  if (h !== -1) end = Math.min(end, h);
  return pathname.slice(0, end) || "/";
}

/** Merge `alternates.canonical` from the page path (resolved via `metadataBase`). */
export function routeMetadata(
  pathname: string,
  metadata: Metadata = {},
): Metadata {
  return {
    ...metadata,
    alternates: {
      ...metadata.alternates,
      canonical: canonicalPath(pathname),
    },
  };
}

export function buildRobots(
  host: string | null | undefined,
): MetadataRoute.Robots {
  if (!isIndexableHost(host)) {
    return {
      rules: {
        userAgent: "*",
        disallow: "/",
      },
    };
  }

  return {
    rules: {
      userAgent: "*",
      allow: "/",
    },
    sitemap: `${PRODUCTION_SITE_ORIGIN}/sitemap.xml`,
  };
}

export function sitemapUrl(pathname: string): string {
  const path = canonicalPath(pathname);
  if (path === "/") return PRODUCTION_SITE_ORIGIN;
  return `${PRODUCTION_SITE_ORIGIN}${path}`;
}